. >> can a silent stroke be a big stroke? >> no >> silent by definition means it's unobserved? >> that's right. it doesn't show up clinically. >> it doesn't show up clinically or behaviorally? >> well, it will show up behaviorally. >> how? >> they will lose interests in things, sit in a room and not talk. >> how about dizziness? >> it could be a sign of anything, a sign of regular or silent stroke. >> how do you learn whether you are stroke prone? >> family history, whether you're hypertensive, whether you have heart disease. >> how about the testing here where the blood gets up to the brain. >> right. >> what do they call that? >> ka rod -- carotid artery. >> should an ultrasound be done? >> if people have an ischemic attack, they may have a carotid artery c collusion. >> do you think that exam should be done regularly? >> i don't think it should be done unless you have symptoms. >> are you going to charge me for this? the -- now, the stroke is not the first step towards alzheimer's, is it? >> no, it is a totally different t